Answers for "chartjs single label for all data"

chartjs y axis prefix

var options = {
    scales: {
        yAxes: [
            {
                ticks: {
                    callback: function(label, index, labels) {
                        return label/1000+'k';
                    }
                },
                scaleLabel: {
                    display: true,
                    labelString: '1k = 1000'
                }
            }
        ]
    }
}

chart.js line chart multiple labels

const myChart = new Chart(ctx, {
    type: 'doughnut',
    data: {
        datasets: [{
            data: [1, 2, 3, 4, 5],
            backgroundColor: [
                'green',
                'yellow',
                'red',
                'purple',
                'blue',
            ],
            labels: [
                'green',
                'yellow',
                'red',
                'purple',
                'blue',
            ]
        }, {
            data: [6, 7, 8],
            backgroundColor: [
                'black',
                'grey',
                'lightgrey'
            ],
            labels: [
                'black',
                'grey',
                'lightgrey'
            ],
        },]
    }
  //....